Conventional closure ring assemblies for drums include a split closure ring having adjacent ends with lugs on each end. One of the lugs has an unthreaded hole and the other lug has a threaded hole for receiving a conventional bolt. When the lid of the drum is secured to its opening, the closure ring is placed around the lid and the bolt is inserted through the unthreaded hole of one of the lugs to engage the threaded hole of the other lug. As the threaded bolt engages the threaded hole, the ends of the closure ring are drawn together to tighten the closure ring around the lid and the drum.
Organizations have developed packaging standards that require compliance with certain vibration, drop and hydrostatic tests to ensure that the drums remain secure and leakproof during transit. Typically, because of the excessive radial clearance between the tie bolt and the enlarged opening of the unthreaded lug, the ends of the closed split ring are prone to separation and movement under impact. This causes ring distortion and seal failure eventually leading to leakage, container failure and possible contamination of both the storage container and its surroundings.
A number of closure ring assemblies have been proposed to overcome the common problems associated with their designs. For instance, in the case of U.S. Pat. No. 5,584,410, a threaded jam nut is mounted on the bolt between the two lugs to prevent unwanted radial movement between the unthreaded lug and the bolt when the split ring is closed. The jam nut is included in the assembly to secure the unthreaded lug between the bolt head and the jam nut to aid in withstanding impact forces. Other designs have been provided to achieve a seal for the open-headed drum that prevents against leakage of the contents, such as those disclosed in U.S. Pats. Nos. 3,907,349; 5,193,864; 5,215,206 and 6,435,576. In the case of the '864 patent, the common problem of undesired movement of the bolt in the unthreaded hole of the lug which can disrupt the sealed relationship between the lid and the drum is addressed by employing a bolt head which is tapered to cooperate with the tapered, unthreaded lug. When the bolt head is drawn into engagement with the unthreaded lug, it causes a guided wedging action and a tangential alignment movement between the lugs and ring ends, with locking nuts adjusted to set the bolt for the desired tension of the locking ring. In the case of the '576 patent, the problem of undesired radial and axial movement of the closure ring is addressed by designing a bolt with a slip sleeve which is flush with the periphery of a large unthreaded hole. The sleeve thereby reduces the movement that is allowable within the large threaded hole to secure the connection of the bolt to the lugs and reinforce the closure ring connection to the drum.
While the designs of existing patents have sought to address and overcome the common problem discussed above, there still remain difficulties with the conventional closure ring assemblies in achieving a tight connection between the closure ring and the drum, thereby complying with vibration, drop and hydrostatic test standards.
Notwithstanding the efforts to achieve tighter connections between the closure ring and the drum with the prior designs described above, a continuing need exists to provide a more secure connection.